a #hardware #oscillator #simulation doing voltage-controlled PWM with an opamp, three resistors, and a capacitor. Based on a figure from Horowitz & Hill, their first example in the Oscillators chapter.
Another #hardware #oscillator #simulation doing voltage-controlled PWM, this time with linearity — the output PWM signal very nearly averages the input voltage. Basically a first-order sigma-delta converter I guess. But sometimes the simulation shows the PWM output not being very PWMy; it occasionally dramatically shifts frequency or hangs out at intermediate voltages for a while, and I don’t understand why. Presumably an additional output stage would clean this up. This version hangs out in the hundreds of kHz, depending on the duty cycle. It uses two op-amps, four resistors, and two capacitors, and has a rise time (10% to 90%) of around 50 μs. But it uses a ridiculous amount of power, like ten or twenty milliwatts.